School districts in L.A., New York, Chicago, Dallas, Miami and Orlando, Fla., plan to announce Thursday efforts to use their collective clout — 2.5 million daily meals served and $530 million annually spent — to make wholesome food a national standard. The districts are also aiming for more eco-friendly practices...Now, by joining forces, the alliance members hope to move the market and eventually enlist other school districts in the crusade."